Referring to the image presented on the last slide of a potato field in Idaho apparently stretching to the foot of distant mountains a questioner asked whether such a landscape is desirable. But in the area where the photograph was taken the natural vegetation is treeless prairie with deep fertile soils where, if nowhere else, expansive monoculture would make sense. Modern technology could prevent landscapes which are not like that from becoming like that by improving productivity in the large scale monocultures that take place there.
The PVY resistance trait inserted in the potatoes is more for the protection of the seed producers against decertification. It becomes problematic at secondary not primary infection. When the growers see the difference they too may attach more importance to PVY resistance, although at first sight it is certainly not the biggest problem for them.
The virus strains probably only appear stable despite the occurrence of a lot of recombination because their environment is stable. It has been possible to detect PVY recombinants in 25% of second generation untransformed plants, and lower rates (1 in 300) with other viral strains. This high level is not just to do with recombination frequency, but with the fact that the environment of the virus is changed by introducing the original transgenic and the virus continues to evolve in its new circumstances. Even if the recombination is not as high as 1 in 4 but is, say, 1 in 500,000,000 it would still be a threat for product failure. As with insect resistance, some kind of resistance management plan might be needed for virus resistance. We know that viruses recombine - that is natural. The significance of viral resistance loss is not agronomic disaster, but product failure of one product for a one company. To avoid the risk of taking away this new tool for the grower we need to know more about resistance management. We could follow the example of use of chemical controls. Widespread use of organophosphorus compounds has been replaced by a variety of chemical agents in an integrated pest management systems. This philosophy could be adapted to integrated resistance management. It would mean that just using a single resistant potato, e.g. Monsanto's NewLeaf Plus, may not be the way ahead. Such a variety is, however, only a first tool that needs to gain acceptance. It cannot replace other aspects of good plant husbandry such as integrated pest management.
The role of environmental factors in the deployment of transgenics was illustrated by the transgenic Bt cotton example in southern USA. The 1997 season saw a big increase in maize cultivation next to transgenic cotton. More maize was cultivated than usual leading in some areas to a forty fold increase in the insect 'pressure' compared with what happens in a typical season. For the insect to be killed by the transgenic they need to eat a bit of the plant. As a result of the huge rise in insect numbers there was visual damage. The growers still sprayed less insecticide in those areas and had a higher yield. A lot of non-factual publicity was spread around as a result of this event. It happens that such alleged setbacks and even erroneous stories are widely publicised, but when the corrections are issued, even when confirmed by independent scientists, it hard to get correspondingly comprehensive publicity. A Swiss non-governmental organisation is still perpetuating in print the falsehood that the Bt cotton was a flop.
Another factor that was at work in the cotton story is that some insects ate the pollen of the cotton flowers where the Bt toxin gene is not expressed. They then survived until a sufficiently late stage of development when they became no longer susceptible to the toxin. It was shown in 1997 that although the Bt cotton was claimed to be resistant to three insect pests, two survived eating it because the toxin level was not high enough to kill them. Recent work shows that beneficial insects are also harmed by Bt toxin producing plants. Laboratory studies have also shown that high levels of Bt can interfere with the sense of smell of bees, thus bringing the risk of interference with their location offood plants. However, it has not yet been proved that Bt levels reached in the field or hive can produce the same effect.
Bollgard cotton was designed to be resistant to tobacco bud worm and was found to be partly resistant to boll worm. It had no activity against boll weevil. In the large scale commercial field trials the spectrum of resistance and the control level was not stated clearly enough to prepare the growers for auxiliary control measures. Where, there is a high boll worm pressure, the grower has to spray. That message did not get from the entomologists studying the transgenic cotton to the field sales force. A further misrepresentation that has arisen concerns the reported boll drop. This was due to the exceptionally cold and wet spring which produced the same effects in the fields of non-transgenic cotton in the same areas.
The Bt potato, more by luck than design, takes half the nitrogen than its non-transgenic counterpart. There is potential for further breakthroughs with transgenics in the area of minimising the inputs of artificial fertilisers. This will help reduce lake and sea algal blooms due to excessive fertiliser use and runoff.
An impression given that the viral spectrum in nature is constant was challenged by a member of the audience. Another confirmed the emergence of a new viral strain within the last ten years. A way to complement the approach of transgenesis would be gradually to move away from using monocultures. It was pointed out too that the potato beetle problem was caused by the introduction of monocultures. The argument that genetic engineering will perpetuate monocultures is a myth. The systemic resistance possibilities are only just now developing and can be integrated into mixed variety cultivation. Any objection that systemic resistance is unwelcome in a food product needs to be seen against the example of the apple. If the apple had to go through a modern regulatory process it would be rejected on the grounds of the content of toxic and carcinogenic substances in its skin. There is no black and white for the future of agriculture. We need a strong genetic engineering lobby which also has a clear ecological vision. The latter aspect is true all the more with the growing trend over the last ten years of biotechnology companies closing or merging leaving just three or four in the field. We then become very dependent on the ethics of that small group. When we listen to the kind of approach with transgenics put forward in today's talk one is reassured, but when one hears Novartis' approach or what they are doing it is less reassuring. Even without genetic engineering, however, it is those same three or four companies that sell the world's crop protection chemistry. They support the best science they can get in academic laboratories. Companies which do good for the environment will be rewarded in the market place.